Apparatus for treating metals



May 3, 1938. E. w, SMITH APPARATUS FOR TREATING METALS Filed Oct. 17, 1935 2 Sheets-Sheet l FIG. 1

FIG. 2

INVENTOR.

EDWARD W. SMITH ATTORNEY.

May 3, 1938.

E. W. SMITH APPARATUS FOR TREATING METALS Filed Oct. 1'7, 1935 2 Sheets-Sheet 2 Patented May 1938 t a 2,116,367

UNITED STATES PATENT OFFICE anus-z Y APPARATUS FOR TREATING METALS Edward W. Smith. Melrose, I, a-ignor to Submarine Signal Oompany, Boston, Mala, a corporation of Maine Application mm 11, 19st. Serial No. 45,442

u can. (cue-s1) The present invention relates to a process and brating the crucible it may be vibrated vertically apparatus for the treatment of metals. In paralong its vertical axis. ticular the present invention relates to a process The method of vibrating the crucible torsionand apparatus for treating molten metals to obally is preferable because a smaller absolute 5 tain afine grain structure in the solidified metal. velocity of the crucible is required than with 5 In the manufacture of steel and other metals vertical vibrations. With this torsional method or alloys it is often highly desirable to obtain a of vibration the shearing action between the solidification of the metal'with a very fine grain molten metal and the crucible or solidified metal structure. This, for example, is of great imtakes place in a direction perpendicular to the portance in the manufacture of stainless steel. direction of cooling at all times between planes 1 It is also of great importance in the production of metal of different temperatures. of cast zinc ingots which are used as the primary An important point to be observed is that relsource of metals for rolling out the zinc plates ative motion must be obtained between the fluid used for etching in the printing industry. metal and the crucible or solidified metal to pro- According to the present invention the molten vide the necessary shearing action. The vibra- 16 metal after being poured into a moldor crucible tion must thus have a sumcient velocity to bring is vibrated while it is cooling. When molten about this result. In case the mold is to be vimetal is poured into a mold and allowed to cool, brated vertically, precautions must be taken to the cooling is accomplished by a crystal formasee that the frequency and amplitude of vertical tion which begins on the inside surface of the motion are such as to ensure a velocity of mo- 20 mold and develops towards the center. Under tion of the crucible which is greater than that the ordinary quiet cooling conditions a series of which would be attained by the molten metal relatively large crystals are thus produced and under the influence of gravity alone. the ingot tends to be'relatively weak at the cen- The vibration of the cooling crucible or mold ter. According to my invention I bring about a with respect to the molten liquid may be carried 25 continuous relative movement of vibration of the out with any suitable vibratory apparatus. Howmolten liquid with respect to its container. The ever, I prefer to use a vibrating systenrwhich in vibration may be obtained by oscillating the itself is resonant at the desired frequency. mold or crucible preferably about its vertical Suitable forms of vibrating apparatus are axis or along its vertical axis. With the crucible shown in the accompanying drawings in which 30 in torsional vibration about its vertical axis the Fig. 1 is a sectional elevation of an apparatus for molten metal will tend to remain quiet, the torslonally vibrating a mold or crucible; Fig. 2 crucible alone moving. is a horizontal section on the line AA of the Under these conditions any crystals which apparatus shown in Fig. 1; Fig'. 3 is a horizontal form will have to form on a surface which is section on the line 3-3 on the device shown in moving with respect to the molten metal from Fig. 1;- Fig. 4 is a vertical section of an arrangewhich they must come so that there is at all times ment for vibrating a crucible or mold in a vera shearing action on any crystals which form tical direction; and Fig. 5. is a modification of which tends to break them up and thereby pro- F18. 4. vides a finer structure in the solidified mass. The The mold or crucible i in Fig. 1 is preferably 40 relative motion between the molten metal and circular in cross section and cylindrical or conical the crucible takes place continuously until the in shape. It is secured to a small table 2 by metal is entirely solidified since each layer which locking screws 3 which hold the crucible securely cools on the inside of the crucible will in effect to the table 2. Suitable heat-insulating material provide anewsurface for the growth of each new separates the table from the frame 5. The layer of crystals. Crystal growth under these latter is supported on a platform 8 by means of conditions results in a more homogeneous mass roller or ball bearings I and itself supports and of smallcrystals rather than in a series of rela- I is rigidly secured to the field pieces 21 of an tively large crystals as is the case where no vibraoscillatory motor. The platform 6 is supported tion is applied. upon a base 8 by ball bearings I II. A shaft l i It willbeevident that vibrations maybe applied is secured to the platform 6 and its lower end in other modes than by the torsional vibration projects into a well if in the base 8. Ball bear- 0! the crucible provided relative motion between lngs it provided in the well I! and ball bearings the crucible and the molten metal is always obl4 suitably mounted in the upper part of the tained. For example, instead of torslonally viframe 5 serve to keep the shaft II in a vertical position. Rlgidly secured to the shaft H are an armature l5 and a spring 16. The spring I! is spiral in shape and is best seen in Fig. 3. It will be seen that one end of the spring is secured by rivets l6 to a collar or flange II on the shaft ll while the other end of the spring is secured by rivet l9 to the frame 6. The arrangement of the armature and the pole pieces are shown in Fig. 2.

It will be noted that there are four pole pieces 24, 25, 26 and 21 which are formed by laminations held together by the bolts 6. Each 01 the pole pieces is surrounded by a coil 26 whereby the magnetic circuit is energized. The armature I6 is separated from the poles by an airgap of suitable dimensions and may conveniently be provided with two windings which are axially disposed around the armature and which are at right angles to one another. It will be clear from Fig, 2 that if the coils 23 on the poles are properly connected together, the direction of flow of the flux can be made to be from poles 24 and 21 to poles 25 and 26, respectively, with a given direction of flow of the current through the windings on the armature. It will also be clear that when current flows through the portion 24' of the windings nearest to pole 24 in a direction perpendicular to and towards the plane of the paper, it will be flowing in a direction perpendicular to and away from the plane of the paper in that portion of the winding which is nearest pole 26; thus when the direction of the flow of flux in poles 24 and 21 is through the armature l5 and toward poles 26 and 26, the passage of current in the direction away from the plane of the paper in the portion of the winding designated as 26' will tend to produce a counter-clockwise rotation of the armature IS. A similar tendency to counter-clockwise rotation will be brought about by the currents in the other windings of the armature.

If the armature coils are properly connected in series with the coils on the poles, the flow of alternating current through the system will always tend to produce a counter-clockwise rotation of the armature. This force will be such as to tend to wind up the spring l6. When the alternating current commences to decrease, the restoring force of the spring will rotate the armature in a clockwise direction until the alternating current passes through zero and again increases in the reverse direction. This again brings about a counter-clockwise rotation of the armature in winding up the spring. This action results in an oscillatory rotation of the armature and of the frame IS.

The amplitude of this oscillatory rotation or torsional vibration will be a maximum at the resonance frequency of the system which is dependent upon the relative masses of the two major elements of the system and upon, the strength of the spring. The two major masses of the system are obviously the armature and platform member 6, on the one hand, and the crucible and its supporting frame 6 carrying the pole pieces, on the other hand. The amplitude of the torsional vibration at resonance is proportional to the magnitude of the current in the windings and if the two masses are equal, they both will have the same amplitude of oscillation. Furthermore, the frequency of the alternating current which must be supplied to the system to obtain resonance must be one-half of the natural sionally about its vertical axis. Since the inertia of the molten metal within the crucible keeps it substantially at rest, a relative motion is obtained between the walls of the crucible and the molten metal.

Instead of vibrating the crucible torsionally, it may be vibrated in the direction of its vertical axis. For this purpose the arrangement shownin Fig. 4 may conveniently be employed. Here the crucible 3| is preferably of a square or rectangular shape rather than of the conical shape of the crucible shown in Fig. 1, although a cylindrical crucible may also be used. The crucible 3| rests upon a table 32 which is insulated by thermal insulating material 34 from the supporting frame 35. The crucible 3| is secured by means of the screws 33 to the table 32 and the latter, in turn, is secured to the frame 35 by means of the bolts 36. The frame 36 is supported by the spring 31 upon the floor 36 of the building. The springs 31 are so designed that their fundamental and harmonic natural frequencies are different from the operating frequency of the system. This frequency difference is preferably about 20%.

Attached to the frame 35 are pole pieces 33 and a yoke member 40 by means of the bolts 4|. These members form the electromagnetic field of an oscillator whose armature is shown at 42. The armature is fixed to the shaft 43 which, in turn, is rigidly connected to the mass 44 having an upwardly extending flange 45 which just fits within and serves as a guide for the downwardly extending flange 46 which is attached to or forms a part of the frame 35.

The mass comprising the magnetic field system which carries the crucible 31 is coupled by means of the spring 41 to the mass 44 to which the armature is connected. The ends of the armature shaft 43 are fitted to slide within the bearings 48 and 49. When the magnets 39 are supplied with alternating current, they will tend to move by magnetic attraction toward and away from the armature 42. In this manner the crucible 3| is vibrated vertically.

The resonant frequency of the system is determined by the relations between the two masses and the stiflness of the coupling spring 41. The maximum amplitude of vibration will be obtained when the alternating current supplied to the magnets 39 has a frequency equal to one-half the natural frequency of the system. If the two masses of the system be made equal, both will have the same amplitude. By increasing the size of the mass 44, the amplitude of the other mass which includes the crucible 3| may be increased, or vice versa.

A modified form of a vertically vibrating system is shown in Fig. 5. In this figure the crucible carrying frame 35 is rigidly fixed to the armature 42 which is supported directly upon the spring 41. The latter, in turn, is fixed to the frame 50 which in this case carries the field magnets 39 and is rigidly fastened to the floor of the building or other support 38. The vibratory system in this case comprises the substantially infinite mass 38 which is coupled through the spring 41 to the mass member comprising the armature and the crucible. ment is somewhat simpler than that shown in Fig. 4, but it must be mounted upon a very firm base 38 in order to avoid any transfer of energy thereto.

While I have described an apparatus for torsionally and vertically vibrating the mold or This arrangecrucible containing the molten metal, it will be evident to those skilled in the art that modifications of the arrangements shown may be made without departing from the spirit of the invention, and, furthermore, it will also be evident that if desired the mold may be vibrated in a horizontal direction and that the apparatus shown may readily be modified for this purpose.

Having now described my invention, I claim:

1. Apparatus for imparting rotational oscillations to a mold for molten metal comprising a mass member rigidly fixed to said mold, electromagnetic field elements secured to said mass member, a base, means for rotatably mounting said mold and connected elements upon said base, a second mass member rotatably mounted on said base, a shaft secured to said second mass member, an electromagnetic armature secured to said shaft and adapted to cooperate with said field magnets and spring means mechanically coupling said armature shaft and said first mass member.

2. Apparatus for rotationally oscillating a container for molten metal comprising, in combination, therewith a table structure for supporting the same adapted to permit it to oscillate freely, an independent mass member having a magnitude at least substantially equal to the mass of said container when filled plus associated elements, means for supporting said mass member so that it is free to oscillate with respect to said container and resilient means adapted to provide between said container and said mass element a restoringforce sufiicient to make the system resonant at the desired frequency of oscillation.

3. Apparatus for rotationally oscillating molten metal including a container therefor, means for supporting the same comprising a base member,- a supporting frame to which said container can be fastened, bearing means for supporting said frame .on said base so as to be free to oscillate, an independent mass element having a magnitude of substantially the same order as the mass of said container when filled plus the elements associated therewith, bearing means for supporting said mass element upon said base so as to be free to oscillate independently of said container supporting frame, resilient means coupling said mass element and said frame and adapted to provide a restoring force sufiicient to make the natural frequency of the system equal to the desired vibration frequency and means for imparting rotational vibration impulses to said system.

4. Apparatus for rotationally oscillating a mold for molten metal comprising an oscillatory electric motor having ar'rnature and field elements, a stationary base member, means for supporting both said elements upon said base so as to be freely oscillatable with respect to the base and to each other, means for rigidly connecting said mold to one of said elements, separated mass means rigidly connected to said second element and having a mass such as to make the entire spect thereto, an electromagnetic system having field and armature elements for producing rotational oscillation energy, one of said elements being mechanically fixed to said crucible supporting means, means for supporting said second element upon said base so as to be free to oscillate with respect thereto and with respect to said first element, a separated mass element mechanically fixed to said second element and of a magnitude sufiicient to make the combined mass of the elements connected to it at least substantially equal to the combined mass of the crucible when filled and the elements connected to it and resilient means adapted to provide a restoring force to make the system oscillate at a natural frequency equal to the desired frequency of oscillation.

6. Apparatus for vibrating molten metal at high velocity comprising a resonant vibratory system composed of a single freely vibratable mass element, an elastic element and a stationary second mass element whose mass is substantially infinite relative to thefirst mass element, said elastic element being fixed at one end to one of said mass elements and at the other end to the other of said mass elements, the first mass element including the molten metal, a container therefor and ancillary elements adapted to move therewith, said elastic element having suflicient elasticity to make the vibratory system resonant at the desired frequency of vibration and means for supplying vibratory energy to vibrate the system at the said resonant frequency.

7. Apparatus for vibrating molten metal at high velocity comprising a resonant vibratory system composed of two freely vibratable independent mass elements and an elastic element fixed at one end to one of said mass elements and at the other end to the other of said mass elements, the first mass element including the molten metal, a container therefor and ancillary elements movable therewith, the second mass element being a compensating mass, said elastic element having sumcient elasticity to make the vibratory system resonant at the desired frequency of vibration and means for supplying vibratory energy to vibrate the system at the said resonant frequency.

8. Apparatus for vibrating molten metal at high velocity comprising a resonant vibratory system composed of a single freely vibratable mass element, an elastic element and a stationary second mass element whose mass is substantially infinite relative to the first mass element, said elastic element being fixed at one end to one of said mass elements and at the other end to the other of said mass elements, the first mass element including the molten metal, a container therefor and ancillary elements adapted to move therewith, said elastic element having sufficient elasticity to make the vibratory system resonant at the desired frequency of vibration and electromagnetic means for supplying vibratory energy to vibrate the system at the said resonant frequency including armature and field elements, one of said elements being fixed to said first mass and the other of said elements being fixed to said second mass, said elements being positioned to cooperate with each other clectromagnetically.

9. Apparatus for vibrating molten metal at high velocity comprising a resonant vibratory system composed of two freely vibratable independent mass elements and an elastic element fixed at one end to one of said mass elements and at the other end to the other of said mass elements, the first mass element including the molten metal, a container therefor and ancillary elements movable therewith, the second mass element being a compensating mass, said elastic element having suflicient elasticity to make the vibratory system resonant at the desired frequency of vibration and electromagnetic means for supplying vibratory energy to vibrate the system at the said resonant frequency including armature and field elements, one of said elements being fixed to said first mass and the other of said elements being fixed to said second mass, said elements being positioned to cooperate with each other electromagnetically.

10. Apparatus for vibrating molten metal at high velocity comprising a resonant vibratory system composed of two freely vibratable independent mass elements and an elastic element fixed at one end to one of said mass elements and at the other end to the other of said mass elements, the first mass element including the molten metal, a. container therefor and ancillary elements movable therewith, the second mass element being a compensating mass having a total mass substantially equal to the total mass of the first mass element, said elastic element having suificient elasticity to make the vibratory system resonant at the desired frequency of vibration and means for supplying vibratory energy to vibrate the system at the said resonant frequency.

11. Apparatus for vertically vibrating a. container for molten metal comprising a two-mass resonant vibratory system composed of two freely vibratable masses and an elastic element fixed at one end to one of said mass elements and at the other end to the other of said mass elements, one of said masses including the metal, its container and ancillary elements adapted to move therewith, said elastic element having sufiicient elasticity to make the vibratory system resonant at the desired frequency of vibration and resilient means for supporting the said vibratory system, the total mass of the latter and the resilient means forming a second vibratory system, the elasticity of the resilient means being so adjusted that the resonance of said second vibratory system is at a frequency substantially different from the resonant frequency of the first vibratory system.

EDWARD W. SMITH. 

